Hi. I'm using the same system, but I don't really have much experience with it yet. So far I've only done instrument recording, not concerts. But FWIW, I love the thing. In my limited tests so far, believe it or not I actually prefer the sound of 406x -> dpa bat box -> Oade modded R1 line-in, to the same chain using the MMA6000 instead of the bat box. I know that "shouldn't be", but to me it sounds more dry, clear and defined, and not quite as rich and boomy. I can't find my notes on the settings, but as I remember, these observations were in proportion to the amount of MMA6000 I dialed in to the equation. But please keep in mind a few caveats: 1) I don't have anything to compare it to; 2) These results would be expected to be very instrument specific, and this was a very rich, though not quite "boomy" instrument; and 3) I've only listened back through earbuds, which are a little bass-heavy.
So basically, these results are meaningless, but I just thought I would chime in out of solidarity for the gear.
I've also recorded 2 week long conferences at 192k mp3, (maybe a total of 60 hours?), using no mics (just the built-in ones) for total convenience – just crank the input level to max and throw it on the desk. Wow. The fidelity is totally audible, and I haven't dumped anything off the 4G card yet – room to burn.
I will pick up a micro track if it turns out to be a better unit, but I must say, the convenience of this thing and the built-in mics are a big plus for me.